With recent advances in technology, mobile phones, digital cameras and other portable electronic devices continue to flourish. In order to satisfy the thinning tendency of the mobile phones and the digital cameras, the demands for compact image sensor modules are increased. Meanwhile, with technological advances and size reductions of image sensing elements, such as charge coupled device (CCD) or complementary metal-oxide semiconductor image sensor (CMOS image sensor), to correspondingly reduce the length of the optical lens installed inside of the image sensor module is needed.
To avoid from shooting with poor quality, while reducing the length of the optical lens, the optical lens should still have great optical performance. Therefore, the amount of lens of the conventional optical lens increases gradually from 2-3 for reducing aberration and reaching the resolution which fits the imaging sensing element. However, to excessively increase the amount of the lens will cause the length of the optical lens to be too long. Therefore, how to reach balance between the length and optical performance of the optical lens is a problem in optical lens design.